President Clinton announced a new initiative in 1998 that sets a national goal of eliminating longstanding disparities in health status that affect racial and ethnic minority groups. Asian Americans and Pacific Islander (AAPIs) are often excluded from analyses of health disparities due to their small numbers. When included in studies, AAPIs are commonly grouped into a single category, despite the tremendous diversity among AAPIs sub-populations and, as a result, little is known about their treatment patterns and outcomes of care. Because AAPIs are highly concentrated in specific geographic regions, regional data collection efforts are the most efficient way to gain information about AAPIs, particularly AAPI subgroups. Hypertension affects approximately 1 in 5 adults in the US. Patient non-compliance with pharmacological treatment has consistently limited the effectiveness of these anti-hypertensive medications and increased the risk of cardiovascular events. Using quantitative and qualitative techniques, the proposed study will provide new evidence concerning factors most strongly associated with compliance with anti-hypertensive medications for Japanese (n approximately 7,500), Chinese (n approximately 1,500), Filipinos (n approximately 2,300), and Hawaiians (n approximately 1,925) through the analysis of existing administrative and patient survey data (1997- 2001). For the proposed study, we have chosen medications for which discontinuation can be used as a proxy for non-compliance because the medications being examined are generally designed for chronic use. Treatment compliance and persistence will be calculated from pharmacy claims data on a possession ratio calculated between the filling of every anti-hypertensive prescriptions. We will attempt to determine to what extent the level of patient copayment and other factors (e.g. age, gender, income, patient-physician communication, morbidity level) affects compliance for each ethnic group. We will also examine the relation between non-compliance and resource utilization, including the number of hospitalizations. Once preliminary results are obtained, we will begin to develop, through focus groups and key informant interviews, strategies for improving compliance for each ethnic group. The infrastructure developed for this project and the collaboration fostered between organizations can be used to support future heath service research endeavors for a wide range of conditions and treatments.